Todos los años _________ escribo una carta romántica a mi esposa para el Día de San Valentín.
Translation:
Every year, [blank] I write a romantic card for my wife for Valentine's Day.
The blank must be filled with a direct object pronoun. The only difference between the two options is one is plural and one is singular. The correct direct object pronoun would be singular, as the direct object (mi esposa) is singular.
Answer:
a. le
Todos los años le escribo una carta romántica a mi esposa para el Día de San Valentín.
